Because the stylist and the customers wore face coverings, health officials said on Friday, they hoped the interactions would lead to “no additional cases”. Those potentially exposed would be contacted and offered testing, officials said.

The potential exposures started little more than a week after Missouri allowed salons to reopen.

The push by Donald Trump and some state governors to reopen most businesses with some public health modifications, such as social distancing and masks, comes as public health officials warn that relaxing restrictions will certainly lead to new outbreaks.

Dr Anthony Fauci, a member of the White House’s coronavirus taskforce, said on Friday that new local outbreaks were “inevitable” as prevention measures are loosened.

But on Thursday, at a visit to a Ford automobile plant in Michigan, the president once again emphasized his focus on getting the economy moving, and the stock market recovered, as soon as possible.

“A permanent lockdown is not a strategy for a health state or a healthy country,” Trump said on Thursday. “Our country wasn’t meant to be shut down.

“This country is poised for an epic comeback,” he said. “Just watch. It’s already happening.”

In debates over how quickly to reopen different businesses across the country, barbershops and hair salons have become a political flashpoint among conservative Americans, with some owners reopening in defiance of public health measures.

In Michigan, a barber who refused to close his shop despite shelter-at-home orders staged a hair-cutting protest at the state capitol which he dubbed “Operation Haircut”, the Lansing State Journal reported.

A hairstylist gives a free haircut as police watch outside the state capitol in Lansing, Michigan, on 20 May.Photograph: Paul Sancya/AP

In Texas, a hair salon owner who was briefly jailed after keeping her business open in defiance of public health orders, and who then refused to apologize in court for what she had done, has been championed by Republican leaders. The Texas senator Ted Cruz visited her salon for a haircut.

In Missouri, county health officials said local residents who had been in the same location as the hairstylist with coronavirus but who had not had direct contact were “believed to be at very low risk”.

While infectious, the same individual also visited a Walmart and a Dairy Queen and made three visits to a local gym, they said.

Missouri’s governor, Michael Parson, did not immediately respond to a request for comment on whether the potential exposures of 91 people at a hair salon would alter the state’s thinking on whether salons and barbershops should remain open during the pandemic.

Missouri’s current public health guidance will expire on 31 May. The state has said it will re-evaluate the plan and may tighten some restrictions or loosen others.